The present invention relates to the field of art of Articulated Arm Coordinate Measurement Machines (further also referred to as AACMM or CMM) as those are for example disclosed in U.S. Pat. No. 5,402,582, U.S. Pat. No. 6,366,831, or WO 03/069267. Those devices comprise a base to be stationed and an arm comprising multiple arm segments connected by articulations. The articulations provide movability to a movable end of the arm, which is opposed to the base, and at the movable end there is a probe head, whereto a measurement probe can be attached. Each of the articulations of the arm is equipped with a sensor to determine a positional information of the articulation, so that the pose of the arm can be determined thereof and position and orientation of the probe head with respect to the base can be determined. The probe head is equipped with at least one, preferably exchangeable, probe head which can be used to measure a point or an area of the object to be examined. During the measurement, the probe head is manually guided by an operator to approach desired measurement points which's geometric coordinate data can be derived according to the pose of the arm.
For example, in U.S. Pat. No. 6,131,299 it is shown to equip such an articulated arm CMM with an alphanumeric display, LEDs and buttons, which are located nearby the handle of the movable end of a CMM. This display indicates the actual position of the arm as numerical X, Y and Z values representing three dimensional coordinates. The operator can thereby see the coordinate values while the workpiece is measured with the probe head.
In order to avoid the requirement of a high level host computer and application software beside the articulated arm, U.S. Pat. No. 5,978,748 shows a user interface and a controller with memory for storing an executable program and reference data, which are mounted to the movable end of an articulated arm. Thereby, the user can be provided with instructions (e.g. inspection procedures), stored CAD data can severe as reference data and a comparison of the actual measurements and the reference data can be done immediately.
U.S. Pat. No. 8,276,286 shows an AACMM with a fully integrated measurement controller and a display located at the base in such a way, that a collision with the measurement arm is precluded.
US 2012/0144685 shows an AACMM where the controller and display is located at the base. It provides a graphical user interface for performing a diagnostics or calibration procedure of the CMM.
A problem with those local computation systems integrated into the articulated arm is, that the lifecycle of such computation equipment is rather short, in particular much shorter than the lifespan of the articulated arm software. According to moors law, the hardware requirements with respect to CPU and memory requirement of the software increases dramatically during the usual lifespan of an AACMM, which is in general much longer than a usual computer software/hardware lifecycle, so that in general the computation unit has to be replaced before the measurement mechanics. Arm-internal intelligence can in general not be easily upgraded or replaced. In particular, those internal systems are specialized designs, which can not be replaced by a plurality of options. That special equipment is also known to be more expensive than off the shelf PC-Hardware. Also, with internal systems, the user is bound to the arms manufacturer for any upgrade or even software update, wherefore a solution with a standard PC and corresponding software that can be replaced and upgraded by products from many vendors and which can be bought at a common store or downloaded from the internet. The mere communication interfaces of computers (like USB, Ethernet, RS232, . . . ) are known to have a much longer lifespan and are often backward-compatible or upgradeable.
Another disadvantage of those prior art designs is that the measurement information provided on an external PC is not always directly visible for the operator during the measurement with the AACMM. In particular an unskilled operator regularly needs guidance on which measurement steps are to be preformed and how to approach all the desired measurement points, preferably in an efficient order, wherefore a standalone measurement protocol document is provided in prior art. In some prior art there might be some display showing the raw coordinate data determined by the machine, but this information is in general rather useless for an inexperienced operator.